August 13-19; Who Was the First Upright Man?

By JOHN NOBLE WILFORD

Published: August 20, 1995

If molecular biologists are right, the evolutionary paths of human beings and apes split 5 million to 7 million years ago. But the fossil record for protohuman species is essentially blank before 3 or 4 million years ago.

So, to fill out the missing stems of the human family tree, paleontologists have been concentrating their searches in African sediments that might bear the remains of the earliest human ancestors.

Now, a team of paleontologists led by Dr. Meave Leakey, following in the famous Leakey tradition of fossil hunting, has hit paydirt in northern Kenya. They reported last week finding fossils of a protohuman species that may have lived as early as 4.2 million years ago. The bones of Australopithecus anamensis are the earliest unambiguous evidence for upright walking, or bipedalism, by a protohuman.

Until now, the oldest evidence has been the 3.6-million-year-old footprints in Tanzania -- discovered by Meave Leakey's mother-in-law, Mary Leakey. (Another new species, Ardipithecus ramidus, found last year in Ethiopia, lived 4.4 million years ago. But its place on the family tree, as a direct ancestor or a side branch, is still being evaluated. JOHN NOBLE WILFORD